Alkali metal dispersions

ABSTRACT

A process for producing dispersions of atmospherically stable, coated alkali metal particles and atmospherically stable, coated alkali metal powders by agitating a mixture of molten alkali metal in a hydrocarbon oil at dispersion speeds, optionally in the presence of a dispersing agent, contacting the molten alkali metal-hydrocarbon oil dispersion, above or below the surface of the dispersion, with up to 3 weight percent anhydrous carbon dioxide while agitating the dispersion for at least 1 minute. The dispersion in oil can be used directly in chemical reactions. The bulk of the oil can be removed from the dispersions to produce oil wet particles, the oil wet particles can be washed with a low boiling hydrocarbon to produce hydrocarbon wet particles which can be dried to produce atmospherically stable powders of coated metal particle The dispersed particles in oil, the oil wet particles, the hydrocarbon wet particles and the atmospherically stable powders can each be used in chemical reactions. After washing and drying, the process produces lithium powders having a surface coating composition containing 0.1-0.3 atom percent lithium, 0.3-0.4 atom percent carbon, and 0.3-0.5 atom percent oxygen. The products of the invention may be used to synthesize organometallic compounds having low color and low soluble inorganic chloride levels.

This application is a continuation-in-part of U.S. Ser. No. 08/210,840,filed Mar. 21, 1994, now U.S. Pat. No. 5,567,474 which is acontinuation-in-part of U.S. Ser. No. 08/019,006 filed Feb. 18, 1993,now abandoned.

This invention concerns a process for preparing novel alkali metaldispersions and metal powders derived therefrom by melting an alkalimetal in an inert liquid hydrocarbon oil medium, agitating the moltenmetal under dispersion conditions to produce a dispersion, contactingthe molten dispersion with carbon dioxide. The dispersion can berecovered by traditional means.

Conventional processes prepare alkali metal dispersions by melting thealkali metal in a hydrocarbon oil and then agitating the molten metal inan inert hydrocarbon oil at dispersion speed in an inert atmosphere,usually argon. Dispersing aids, such as silicon oils, hydrocarbonpolymers, ethers, alcohols, organic acids, carbon black, organic saltsand so forth are used to facilitate rapid dispersion of the molten metaland development of uniform particle size. The finished dispersion iscooled, optionally separated from the hydrocarbon oil by washing themetal with a hydrocarbon solvent of choice and stored under argon.Unless stored under argon or some other inert, protective medium thesealkali metal dispersions, when dry, react with the atmosphere underambient storage conditions and there will be a loss of reactivity anddanger of ignition.

An alternative process forces molten alkali metal and argon through ahigh shear spray nozzle into hexane.

The book "Alkali Metal Dispersions" by Irving Fatt and Marie Tashima, D.Van Nostrand Company, Inc., 1961, contains conventional dispersionprocess details and lists numerous dispersing aids and equipment.Dispersing equipment which can be utilized to produce the products ofthis invention is designed to produce a high tangential shear in thealkali metal-hydrocarbon medium mixture and is described in the book byFatt and Tashima cited above ( pp 41-49). Other conventional reactionequipment such as centrifuges or fluid bed reactors do not provide thehigh tangential shear necessary to produce such metal dispersions andare not recommended.

The present invention provides a process for producing atmosphericallystable alkali metal particles comprising heating, in an inertatmosphere, an alkali metal selected from the group consisting of sodiumand lithium in a hydrocarbon oil to a temperature above the meltingpoint of the alkali metal, agitating the metal in hydrocarbon oilmixture, under dispersion conditions, which mixture optionally containsa dispersing agent, contacting the molten metal-hydrocarbon oildispersion mixture, above or below its surface, for at least one minutewhile the mixture is being agitated under dispersion conditions, with atleast 0.3 weight percent of anhydrous carbon dioxide, based on theweight of the alkali metal and cooling the alkali metal dispersion tobelow the melting point of the alkali metal to produce coated alkaliinetal particles dispersed in oil.

In accord with the present invention lithium and sodium metaldispersions in hydrocarbon oil are readily prepared by heating, in aninert atmosphere, to above the melting point of the metals, atemperature range of 100° to 240° C., about 100° to 150° C. for sodiumand 180° to 240° C. for lithium vigorously agitating the moltenmetal-hydrocarbon oil mixture under high tangential shear (dynamicconditions) for sufficient time to produce a dispersion or emulsion ofthe metal into uniform particles or globules in the hydrocarbon oil.Optionally the dispersion can be prepared by vigorous stirring atdispersion speeds in the presence of a dispersing agent, then contactingthe dispersed metal with anhydrous carbon dioxide gas while maintainingthe high tangential shear stirring at dispersion speeds for a certainperiod of time, at least about a minute, to provide a predeterminedamount of the gas for contact and reaction with the metal. Varying theamount of dispersing agent makes it possible to produce particles havingdifferent particle size ranges.

Typical alkali metal dispersing or "emulsifying" devices, in usecommercially, employ high tangential shear during agitation according toFatt and Tashima (p 49). The anhydrous carbon dioxide of this inventionis added to the molten metal dispersion mixtures of this invention,while the mixtures are under high tangential shear agitation, until0.3-5 weight percent carbon dioxide based on alkali metal has beenintroduced into the mixture. While carbon dioxide is preferablyintroduced below the surface of the mixture, the vigorous agitationconditions necessary to produce dispersions generally gives adequatecontact with carbon dioxide introduced in the gas space above thedispersion mixture. The amount of carbon dioxide introduced should bebetween 0.3-5 weight percent based on the metal. Higher levels ofanhydrous carbon dioxide can be employed but do not appear to provideadditional advantages. Some minimum contact time between the anhydrouscarbon dioxide and metal is necessary, one minute being adequate, and 1to 5 minutes a practical reaction period. Although, according to US Ser.No. 08/210,840, now U.S. Pat. No. 5,567,474, one may prepare thesedispersions using anhydrous carbon dioxide alone (no dispersing agentpresent), better control of the metal particle sizes and their sizedistribution is obtained if one first disperses the metal in thepresence of a suitable dispersing agent, and then afterwards adds theanhydrous carbon dioxide under high tangential shear conditions.

An advantage of the process is that the anhydrous carbon dioxideunexpectedly reacts sufficiently with molten alkali metals, inparticulate or very small molten globule form, suspended in ahydrocarbon oil to form a protective, dispersive coating around themetal particles. This is an unexpected result since Markowitz, discussedbelow, reports that anhydrous CO₂ does not react with dry 100-125 sievelithium metal particles (125-150 microns) up to 250° C. under staticconditions and only slightly with wet CO₂ under these conditions. Wehave found no such impedance to the reactivity of anhydrous carbondioxide with lithium metal under the conditions of the present process.Wet CO₂ is not desirable since it generates hydrogen which may reactwith lithium metal to produce lithium hydride or may be liberated fromthe vessel as a dangerous gas.

It is another object of this invention to prepare organoalkalicompounds, such as organolithium compounds, by utilizing the alkalimetal dispersions and alkali metal powders produced by the process ofthis invention. These organolithium compounds may be alkyllithiums andaryllithiums, lithium dialkylamides, lithium cycloalkylamides, andlithium alkoxides.

Another unexpected advantage of the process is that the large (1-3%)amount of dispersing agent, e.g., oleic acid, ordinarily required tomaintain the metal particles at a desired particle size of 10-50microns, is not required when anhydrous carbon dioxide is added in theprocess afterwards. Generally, amounts of oleic acid required to achievethis particle size range when CO₂ is employed are less than one percent.

On cooling the dispersions produced by this invention to ambienttemperature and removing the hydrocarbon oil medium by washing the metalparticles with a low boiling hydrocarbon of choice and evaporating saidlow boiling hydrocarbon under a stream of dry argon, a lithium (orsodium) metal powder is produced. These powders are relativelyunreactive to the components of the ambient atmosphere and can betransferred through such ambient atmospheres from one container toanother without danger of ignition or loss of chemical reactivity. Thealkali metal powders of this invention are unexpectedly reactive to anumber of organic compounds. Conventionally produced alkali metalpowders exposed to the ambient atmosphere are well known to reactquickly with the components of the atmosphere, rapidly losing activityand occasionally igniting.

Although Markowitz, Journal of Chemical and Engineering Data, Vol. 7,No.4, p. 590, states that "lithium carbonate, probably formed by theover-all reaction,

    2 Li+H.sub.2 O+CO.sub.2 →Li.sub.2 CO.sub.3 +H.sub.2

yields a protective coating on the surface of the metal", he was notable to react dry carbon dioxide (no moisture present) with 100-125sieve (125-150 micron) lithium particles up to a temperature of 250° C.(no indication given that any reaction with CO₂ occurs above 250°C.)whereas the present process readily reacts dry CO₂ with a molten lithiummetal dispersion in hydrocarbon oil at much lower temperatures(190°-210° C.). Further, it should be noted that a temperature of 250°C. or higher is not recommended for metal dispersion preparations sincegenerally considerable decomposition of the hydrocarbon oil can occur.In contradistinction to the present process, the lithium metal particlesused by Markowitz were previously freed of the mineral oil dispersingmedium by washing with hexane and drying in a stream of argon (pp586-587) before being subjected to contact with dry or wet CO₂(Markowitz obviously carries out this prior washing of the metalparticles because he believes that no reaction with the components ofthe atmosphere, such as CO₂, can occur in the presence of a hydrocarbonoil (see page 586, second column) since, before x-ray identification ofhis lithium metal species he mixes each sample with lithium-treatedvaseline, a hydrocarbon oil analog, to prevent atmospheric attack on thelithium metal). Furthermore, this contact of metal particles with CO₂ inthe Markowitz process took place under static conditions. (It should benoted that, under such static conditions, the lithium metal particles ofthe Markowitz process will fuse into a solid mass above the meltingpoint of the lithium metal (183° C.), whereas the lithium metalparticles of the present process will retain their original size to muchhigher temperatures (>200° C.).

Markowitz does not speculate on the reactivity of Li₂ CO₃ --coatedlithium metal particles with organic substrates nor does he evenidentify the nature of any coatings on his carbon dioxide-treatedlithium metal particles.

The surface coating on the lithium metal powders produced by the processof this invention has been found by X-ray photoelectron spectroscopy(XPS) to consist of 0.19-0.22 atom percent lithium, 0.33-0.39 atompercent carbon and 0.36-0.46 atom percent oxygen. These ranges for theatomic components do not correspond to those for pure lithium carbonate(Li=0.33 at %, C=0.17 at %, O=0.50 at %). D.J. David, M. H. Froning, T.N. Wittberg, W. E. Moddeman, Applications of Surface Science, 7 (1981)181-185, state that the results of the reaction of anhydrous carbondioxide with freshly cut surfaces of lithium metal at ambienttemperature (as determined by Auger Electron Spectroscopy) indicate thesurface coating to consist of lithium oxide and lithium carbide, notlithium carbonate. At this point, it is not possible to say,definitively, what is the nature of the compounds comprising theprotective surface coating on the alkali metal powders of thisinvention. Some compositional ranges of these elements on the surface ofthe lithium metal powders of this invention are 0.1-0.3 atom percentlithium, 0.3-0.4 atom percent carbon and 0.3-0.5 atom percent oxygen.

The process of this invention produces alkali metal dispersions havingmetal particle sizes in the range of 10 to 300 microns, and even largersized metal particle powders (to 1000 microns) can easily be produced.On cooling, the resulting alkali metal dispersions of this invention arereadily filtered to remove the bulk of the dispersant hydrocarbon oiland the metal is then washed with hexane to remove residual oil, afterwhich the metal powder is dried. The process can be controlled toproduce various particle size ranges, such as 10 to 50 microns, 10 to300 microns, 50 to 400 microns, 10 to 1000 microns, and so forth.Surprisingly, the resulting dried metal powders ("Dry Pack") areunexpectedly stable to ambient atmosphere for periods up to about anhour allowing their safe transfer in such atmospheres from one containerto another. The lithium and sodium powders of this invention have beenfound to be non-pyrophoric by standard pyrophoricity tests.

Lithium metal particle sizes in the inventive dispersions, prepared inthe hydrocarbon oil of choice, can be varied by adjusting the amount ofdispersing agent (oleic acid) employed, as shown in the tables below.

    ______________________________________                                        Lot no.                                                                              O.A. (%) CO.sub.2 Particle Range                                                                         Av. Particle Size                           ______________________________________                                        10216  0.450    1.5      5-60     30                                          10009  0.346    1.5      10-300   80                                          10005  0.184    1.5      100-300  150                                         10027  0.171    1.7      50-700   300                                         10043  0.151    2.0      400-2000 1000                                        ______________________________________                                    

Notes: (a) Particle ranges and sizes in microns

(b) O.A.=Oleic acid (commercial grade)

(c) (%) of O.A. and CO₂ based on lithium metal.

It was found that the use of 0.368% oleic acid alone, i.e., in theabsence of CO₂, resulted in agglomeration of the metal in the particularlow viscosity hydrocarbon oil of choice under the particular dispersionconditions employed above. Generally, at least about one percent oleicacid is required to produce a satisfactory dispersion with particlesizes under 100 microns in size. The use of CO₂ alone, i.e., no oleicacid present, gave a somewhat broader range of particle sizes and didnot allow for any significant variation in the particle size range, asseen in Tables 3 and 4 (compare to above table). Of course, carbondioxide can be employed with conventional dispersing agents such asoleic acid and generally, one may employ considerably less oleic acidwhen using CO₂.

Sodium metal, incorporated in the lithium must be kept below the alloycomposition, i.e., below 0.88 wt %, in order to prevent thickening orgellation of the dispersion mass during the preparation of conventionallithium dispersions e.g., using oleic acid alone. However, with thesubstitution of carbon dioxide for part or all of the oleic acid, thereis no practical upper limit for sodium incorporation. For example, Table2 shows a 5 weight sodium incorporation, based on lithium, which has notendency to thicken.

A variety of hydrocarbon oils may be used successfully in the presentinvention. The term hydrocarbon oil, as used herein, includes variousoily liquids consisting chiefly or wholly of mixtures of hydrocarbonsand includes mineral oils, i.e., liquid products of mineral originhaving viscosity limits recognized for oils and hence includes but isnot limited to petroleum, shale oils, paraffin oils and the like. Thereare many manufacturers of these useful hydrocarbon oils. Among theseuseful hydrocarbon oils are white oils (highly refined), such as, e.g.hydrocarbon oils like Peneteck, manufactured by Penreco Division ofPennzoil Products Inc., which has a viscosity in the range of 43-59pascal-sec at 100° F. and a flash point of 265° F. (129° C.), Parol 100,which has a viscosity of 213-236 pascal-sec at 100°0 F. and a flashpoint of 360° F. (182° C.) and Carnation white oil (viscosity=133-165pascal-sec at 100° F.; flash pt =177° C.) made by Sonneborn Div. ofWitco. Even certain purified hydrocarbon solvents which boil in a rangeencompassing the melting point of lithium or sodium metal may be used,such as UNOCAL's 140 Solvent (b.p. range=190°-203° C.). In addition,unrefined oils, such as Unocal's 460 Solvent (b.p. range 189°-262° C.) ,Hydrocarbon Seal oil (b.p. 270°-321° C.) and Exxon's Telura 401 (b.p.174°-322° C.) and Telura 407 (b.p. 245-450° C.) may also be used.

Solvents useful in the practice of this invention include aliphatics,especially lower alkanes containing 5 to 10 carbon atoms, aromaticscontaining 6 to 10 carbon atoms and mixtures thereof including petroleumether and other commercially available mixtures of hydrocarbons havingrather narrow boiling ranges.

Coated lithium particles of this invention can also be prepared byspraying (using a high shear nozzle) molten alkali metal into a carbondioxide atmosphere, as into a container having a carbon dioxideatmosphere, and collecting the particles in a solvent such as hexane.

The metal powders of this invention can be dried and packaged insuitable containers under an inert atmosphere, such as argon ("DryPAck"). The powders can easily be introduced into commercial orlaboratory reactions as dry powders or slurried in an inert solvent andintroduced into the reaction as a slurry. The dispersions are of courseuseful in chemical reactions as dispersions in oil, as oil wet particlesafter filtering to remove the bulk of the oil, or solvent wet particlesobtained by washing the oil wet particles with a suitable hydrocarbbosolvent to produce solvent wet particles.

It was further unexpectedly found that the coating on the alkali metalparticles produced by the process of this invention did not retard thereactivity of the metal with alkyl halides, but did protect the alkalimetal from reaction with the ambient atmosphere. It was found thatn-butyllithium could be prepared in an 82% yield from such a lithiumpowder that had been exposed to an ambient atmosphere for a 1 hourperiod One might conjecture that a such a protective coating wouldprevent reactions with such organic substrates from occurring since muchsmaller molecules, such as oxygen and nitrogen, do not react readilywith the coated powders. However, it was found that a normally producedlithium powder (no CO₂), when exposed to the ambient atmosphere for onehour and then reacted with n-butyl chloride, resulted in only a 39 %yield of n-butyllithium. This is an unexpected advantage of producingalkali metal dispersions and powders by the process of this inventionsince, as here indicated, reaction with the ambient atmosphere lessensthe degree of reactivity of alkali metal dispersions, produced byconventional means, with alkyl halides.

Thus, the lithium dispersions and dried lithium powders of thisinvention unexpectedly have been found to be capable of forming avariety of organolithium products in good yields from correspondingorganic chlorides and organoamines. Among these organolithiums are n-,sec-, iso- and tert-butyllithiums, phenyllithium, n-hexyllithium, and2-ethylhexyllithium. Even lithium dialkylamides such as lithiumdiisopropylarnide could be prepared by metalation of the correspondingdialkylamines (see Table 1). Other organic compounds are also capable ofreacting with the metal powders of this invention, such as e.g.,alcohols, esters, aldehydes and ketones.

Lithium powder, generated by the process of this invention , protectedfrom ambient conditions and stored under argon for 30 days, producedhigh (90-95%) yields of n- and sec-butyllithium in hydrocarbon solutionsand such n- and sec-butyllithium possessed remarkably low color,platinum-cobalt colors (APHA) of <25 to <100. Tables 1 and 2 list anumber of organolithium compounds prepared from the lithium dispersionsand powders of this invention and their yields, chloride content, andcolor. The Pt/Co colors of <25 to <100 are to be compared to typicalvalues of Pt/ Co values of 150-250 for typical production runn-butyllithium. The color of the products having colors of <25 uponconcentration to 97 weight % by removing most of the hexane only had acolor of 50 Pt/ Co.

An additional advantage in the use of carbon dioxide coated lithiummetal powders is the striking effect on the chloride content of theorganolithium solutions in hydrocarbon solvent media (prepared fromorganic chlorides) when using the lithium metal dispersions prepared bythe process of the invention. The values for the soluble inorganicchloride in these solutions are substantially lower then produced by aconventional lithium dispersion. The soluble inorganic chloride from thepresent invention varies from <100 to <1000 ppm, depending on whethern-butyllithium or s-butyllithium is being made and the concentration ofthe alkyllithium solution. The same products produced from lithium metaldispersions that do not contain a coating composition of this inventionare higher, in the range of 300 ppm and higher. Lower chloride levelsare associated with clearer product alkyllithium solutions which haveenhanced marketability (see Table 2).

The following examples further illustrate the invention.

EXAMPLE 1 LITHIUM DISPERSION IN PENETECK WHITE HYDROCARBON OIL USINGCARBON DIOXIDE (SURFACE FEED) AS DISPERSING AGENT Experiment No. 7285

Lithium metal 300 g of low sodium grade was charged to a 3 literstainless steel resin flask reactor with a 4" (10.16 cm) top fitted witha stirring shaft connected to a fixed high speed stirrer motor with aflexible shaft and top and bottom heating mantles in a dry atmosphereroom under argon.

The reactor was then assembled and 2.25 g of sodium metal and 90% g ofPeneteck* hydrocarbon oil were added. Peneteck hydrocarbon oil is aproduct of Penreco Division of Pennzoil Products Co. The reactor wasthen heated to 200° C. until the lithium and sodium metals becamemolten.

Stirring was maintained gently and intermittently until all the metalwas completely molten. Then the mixture was stirred at high speed(10,000 rpm) for 5 minutes. Carbon dioxide, 7.74 g, was charged, surfacefed over a 4 minute period while continuing high speed stirring. Thehigh speed stirring incorporated the carbon dioxide into themetal-hydrocarbon mixture. When the carbon dioxide was all added thestirring was stopped, heating mantles removed and the reactor cooled toabout 65° C. before bottling the product dispersion. The metal particlesize range was found to be 10-200 microns.

Details of further examples using the procedure of this example aregiven in Tables 3 and 4.

COMPARATIVE EXAMPLE USING OLEIC ACID AND CARBON DIOXIDE Experiment No.10009

A weight of 12.7 pounds of lithium metal, 0.033 pounds of sodium metaland 34 pounds of Peneteck oil were charged to a 15 gallon stainlesssteel reactor. The mixture was heated to about 190° C. and held thereuntil all of the metal became molten. Intermittent stirring was employedto speed the melting process. High speed shear stirring was begun whenthe metal became completely molten and sustained for two minutes. Thestirring rate was then slowed, 20 grams of oleic acid added, and highspeed stirring continued for an additional 2 minutes before starting CO₂addition . A total of 85 grams of CO₂ was added over a 5 minute period,the temperature rising about 30 degrees. When CO₂ addition was complete,stirring was discontinued, the heating source removed, and coolingapplied. When the temperature reached 150° C. gentle stirring was begunand the temperature lowered to 50° C. before pumping the dispersion outof the vessel. A photomicrograph of the dispersion showed a metalparticle range of 10 to 300 microns, with an average particle size lessthan 100 microns.

EXAMPLE 2 PREPARATION OF DRY LITHIUM POWDER Experiment No. 7222

Lithium dispersion (lot 7218) prepared as in Example 1 above wasfiltered and washed in an enclosed, sintered glass filter funnel (fineporosity) to remove the hydrocarbon oil medium. Filtration to remove thebulk of the oil occurred rapidly, as did the subsequent hexane washings(3). Finally, the lithium metal residue in the funnel was washed oncewith n-pentane, filtered, and the funnel heated with a heat gun toremove traces of solvents. The resulting free-flowing powder wastransferred from the funnel to a tightly capped storage bottle.

A pyrophoricity test Code of Federal Regulations 49--TransportationSection 173.125 and Appendix E (CFR 49)! carried out on this materialshowed it to be non-pyrophoric. An exposure test (Experiment #7231)carried out on a sample of this dry powder placed on-a watch glass andexposed to ambient air conditions; no heat was generated on exposure tothe air nor did any color change occur within 8 hours as occurs withnormally prepared lithium dispersion powders. There was no odor ofammonia, either, as normally occurs due to nitridation of the metal.

EXAMPLE 3 PREPARATION OF n-BUTYLLITHIUM IN HEXANE USING CARBON DIOXIDEDISPERSED LITHIUM METAL POWDER PREVIOUSLY EXPOSED TO AMBIENT AIRExperiment No. 7271

A lithium metal dispersion in Peneteck hydrocarbon oil prepared as inExample 1 with carbon dioxide (#7218) was filtered and the metal washed3 times with hexane, once with n-pentane, and blown dry. A 9.0 gram(1.30 moles) portion of this metal powder was placed in an open Petridish and exposed to ambient air (80% relative humidity) forapproximately one hour. It was then transferred to a reaction flaskalong with 164 mls of hexane and 5 ml. of a 15 wt % n-butyllithium inhexane conditioner and stirred for about 20 min. before starting a feedof 54.6 g (0.584 moles) of n-butyl chloride. The reaction proceeded welland, after 2 hours of post addition stirring, was filtered from theby-product lithium chloride and the latter washed three times with atotal of 120 mls of hexane. The filtrations proceeded rapidly to give awater white, clear solution of a 15 wt % solution of n-butyllithium inhexane (82.3% yield based on n-butyl chloride). This experiment showedthat there was a protective coating on the lithium metal powdersufficient to prevent any significant loss of lithium metal duringtransfer of the powder in air.

EXAMPLE 4 LITHIUM DISPERSION IN PENETECK WHITE HYDROCARBON OIL USINGCARBON DIOXIDE AS DISPERSING AGENT - SUBSURFACE FEED Experiment No. 7505

The reactor and apparatus consisted of a 3 liter stainless steel roundbottom flask with 4" (10.16 cm) opening, a 4"(10.16 cm) head withstirring shaft fixed therein, and connected to a high speed stirrermotor via a flexible shaft and a fixed argon inlet and a stainless steelsintered sparger disc and top and bottom heating mantles. The spargerdisc (2 1/2" 6.35 cm! biscuit type) was fixed directly below the cuttingblade of the stirring shaft and was approximately 3/4" (1.8 cm) off thebottom of reactor.

Lithium metal (350.0 grams) was charged to the reactor in the dryatmosphere room. The reactor was assembled and 2.625 g of sodium andPeneteck hydrocarbon oil were added. The reactor was then heated toabout 200° C. and the contents stirred gently until all metal was molten(approx. 30 minutes). Metal and oil were then stirred at high speed(10,000 rpm) for 4 minutes, then carbon dioxide was fed in through thesparger for a period of 2 minutes. Temperature of the reaction rose 11°C. (from 191-202° C.) when the carbon dioxide was charged. At end of thecarbon dioxide feed, stirring was stopped, the heating mantle wasremoved and the dispersion cooled to about 65° C. before transferring totightly capped storage bottles.

EXAMPLE 5 SECONDARY BUTYLLITHIUM IN CYCLOHEXANE VIA CARBON DIOXIDEDISPERSED LITHIUM METAL Experiment No. 7506

The reactor and apparatus consisted of a 500 ml, 3 necked Morton flask,a Claisen adapter, 125 ml dropping funnel, a stirring shaft with TEFLONblade, stirring motor, and a thermometer probe with an electronic readout.

Lithium metal dispersion (prepared as in Example 1) was hexane washedtwo times and pentane washed twice and dried with argon. The metal wasthen weighed and the experiment conducted using 10% excess lithium(14.42 g or 2.078 moles) and 395 milliliters of cyclohexane solvent.

Cyclohexane was used to transfer the lithium through a transfer tube tothe reactor. Conditioner, 5 ml s-butyllithium in cyclohexane, was addedand the mixture stirred for 15-30 minutes. One to three mis of sec-butylchloride was added which raised the temperature from ambient to around34° C. When the temperature began to drop, a slow s- butyl chloride feedwas started. The sec-butyl chloride was fed over one hour and forty-fiveminutes adding a total of 87.4g (0.944 moles) and the reactiontemperature was maintained between 32°-37° C.. The reaction was stirredfor 1.5 hours, then filtered through a 500 ml medium fritted filterusing inert diatomaceous earth filter aid. The solution filtered veryfast (less than 5 minutes).

The final solution yield was 89.3%, C-bound lithium was 98.2% with lessthan 10 ppm soluble inorganic chloride ion in solution.

Further examples are given in Table 4.

EXAMPLE 6 SODIUM DISPERSION IN PENETECK HYDROCARBON OIL USING CARBONDIOXIDE AS DISPERSING AGENT Experiment No. 7511

Into a 500 ml Morton flask fitted with a high speed stirrer and gasinlet tube was placed 60 grams of sodium metal and 140 grams of Peneteckhydrocarbon oil. The contents of the flask were heated to 108° C. andstirred until all of the metal became molten. The mixture was thenstirred at high speed (10,000 rpm) for 3-4 min. and the carbon dioxidegas feed begun. A total of 1.0 grams of carbon dioxide (1.7 wt % basedon the metal) gas was fed into the mixture. The temperature of thereaction rose 3° C. within the first few seconds of the feed and thenheld constant for the remainder of the feed. Then, stirring wasdiscontinued and the mixture cooled to room temperature. Part of theresulting dispersion was washed with hexane and pentane, then blown drywith argon to convert it to a dry, free-flowing powder. A small portionof the dry powder was placed on a watch glass in the hood. It did notignite. It took approximately 10-15 min. before the powder turned-white.The CFR 49 pyrophoricity solid test was negative. A photomicrograph ofthe solid dispersion showed particle sizes in the 1 to 200 micron rangewith most in the 50-100 micron range.

EXAMPLE 7 PREPARATION OF n-BUTYLLITHIUM IN HEXANE VIA CARBON DIOXIDEDISPERSED LITHIUM METAL Experiment No. 7851

The reactor and apparatus was as described in Example 5, plus heatingmantle, and reflux condenser.

The lithium metal dispersion prepared as in Example 1 was hexane washedtwice and pentane washed once and dried with argon. The metal was thenweighed, 12.10 g (1.743 moles).

Hexane, 310 milliliters, was used to transfer the lithium through atransfer tube to the reactor. The hexane-lithium mixture was heated toreflux (dry ice/hexane in condenser) and dropwise feed of n-butylchloride begun. The reaction proceeded instantaneously (refluxing) andthe source of heat was removed. Then 73.4 g of n-butyl chloride (0.7924moles) was fed in over a 40 minute period, the reaction heat controlledstrictly by the rate of reflux. The reaction mixture was allowed to coolto ambient (stirring) over a 2.5 hour period. The mixture was filteredand the lithium chloride residue washed three times with hexane (50 mleach) over a 25-30 minute period. The combined filtrate and washingsweighed 256.4 grams. A sample of the clear, water white (Pt/Co=<25 waterwhite solution) product solution was assayed for total containedalkalinity and found to contain 2.94 meq/gram of solution 18.83 wt % n-butyllithium. The yield of n-butyllithium was 95.2%. Removal of thehexane solvent under vacuum gave a 97 wt % product which was clear andyellow in color (Pt/Co=50 ASTM=D1209). Further examples are given inTable 4.

The above results can be compared to a similar run using a lithiumdispersion prepared with oleic acid alone as a dispersant (experimentnumber 7813) where the resulting product solution was yellow (Pt/Co=175)and the concentrated product (97%) was yellow (Pt/CO=300) and the yieldwas 94.7%.

From the foregoing disclosure and examples it is evident that it ispossible, according to the invention, to produce a stable alkali metalpowder formed by heating an alkali metal in a hydrocarbon oil to atemperature above the melting point of the alkali metal, agitating thethe molten alkali metal, maintaining agitation under conditionssufficient to disperse the alkali metal into small molten particleswhile contacting the alkali metal with at least 0.3 weight percent ofanhydrous carbon dioxide for at least one minute to disperse the moltenalkali metal and recovering a stable coated alkali metal powder havingparticle sizes in the range of 10 to 1000 microns in the form of a drypowder.

                  TABLE 1                                                         ______________________________________                                        USES OF LITHIUM DISPERSION MADE                                               WITH CARBON DIOXIDE STABILIZER                                                Lot No.                                                                              RLi        Init. Agent                                                                            % Yield                                                                              Remarks                                     ______________________________________                                        7224   n-Butyl    none     94     Dry pack day 1                              7231   n-Butyl    none     90     Dry pack day 6                              7253   n-Butyl    none     91     Dry pack day 32                             7261   s-Butyl    none     92     Dry pack day 1                              7262   s-Butyl    none     90     Dry pack day 35                             7292   2-Et Hexyl none     42     (a)                                                (heptane)                                                              7230   t-Butyl    1 g sand 73     (b)                                                (pentane)  per g Li                                                    7302   Phenyl (DBE)                                                                             IPA      94     (c)                                         7309   LDA        none     97     (d)                                         7288   n-Hexyl    none     88                                                 ______________________________________                                         (a) Lithium dispersion prepared with oleic acid as dispersant did not         initiate in heptane.                                                          (b) Lithium dispersion prepared with oleic acid as dispersant gave an 80%     yield.                                                                        (c) Run did not initiate on its own                                           (d) Reaction gave results equivalent to that using lithium dispersion         prepared from oleic acid.                                                     DBE dibutyl ether                                                             IPA 2propanol                                                                 LDA Lithium diisopropylamide                                             

                  TABLE 2                                                         ______________________________________                                        Effect of Carbon Dioxide Dispersed Lithium on                                 Final Chloride Content of RLi in Hydrocarbon Solution                                                           Soluble                                     Run             Li Dispersant     Inorg. Color                                No.   Alkyllithium                                                                            (W %        Yield %                                                                             Cl. (ppm)                                                                            (Pt/Co)                              ______________________________________                                        7506  SBL(1)    CO2 (0.9)   89    <10    <25                                  7515  SBL       CO2/5% Na   88    <11    <25                                  7523  SBL       CO2 (1.3)   87    33     <25                                  7525  SBL       CO2 (2.6)   89    41     <25                                  7526  SBL       CO2 (3.9)   84    46     <25                                  7527  NBL(2)    CO2 (1.4)   89    87     <25                                  7529  NBL       CO2 (0.9)   90    126    <25                                  7530  NBL       CO2/5% Na   83    58     <25                                  7551  NBL       CO2 (3.2)   87    193    <25                                  --    NBL       Oleic Acid (1.0)                                                                          --    300(3) 175                                  ______________________________________                                         (1)Cyclohexane solvent                                                        (2)Hexane solvent                                                             (3)Typical value                                                              SBL secondary butyllithium                                                    NBL normal butyllithium                                                  

                  TABLE 3                                                         ______________________________________                                        LITHIUM/CO2 DISPERSIONS IN PENETECK OIL                                       EXPER-           PRE-CUT        CO2    PARTICLE                               IMENT  REACTOR   TIME     CO2 % FEED   SIZE                                   NO.    SIZE      (Min)    (WT)* TIME (Min)                                                                           (Microns)                              ______________________________________                                        7174   500 ml    3        --    start to                                                                             10-200                                        18 g Li                  finish                                        7179   500 ml    3        5.2   2      20-300                                        30 g Li                                                                7187   500 ml    3        3.0   1      20-300                                        30 g Li                                                                7218   3 l.      4        1.8   3      10-200                                        355 g Li                                                               7283   3 l.      10       1.0   1      10-500                                        300 g Li                                                               7285   3 l.      5        2.0   4      10-200                                        300 g Li                                                               7290   3 l.      5        3.0   6      10-500                                        300 g Li                                                               7291   500 ml    9        1.0   0.5    20-300                                        30 g Li                                                                ______________________________________                                         *Surface feed                                                            

                                      TABLE 4                                     __________________________________________________________________________    CO2/LITHIUM DISPERSIONS IN PENETECK OIL                                       Dispersions                                                                            CO2                                                                              CO2 Time                                                                           T (°C.)                                                                    Particle        Alkyllithiums                                                                        Filter Rate                       Run No.                                                                            % CO2                                                                             g/min                                                                            (min.)                                                                             (feed)                                                                            Size                                                                              Comments                                                                             Run No.                                                                            Type                                                                             Yield                                                                             ml/min                            __________________________________________________________________________    SURFACE FEED                                                                  7283 1.29                                                                              3.87                                                                             1    11  <200       7523 SBL                                                                              87.8                                                                              100                               7469 2.20                                                                              2.16                                                                             3    13  20-300     7470 SBL                                                                              86.5                                                                              33                                7285 2.58                                                                              1.94                                                                             4    --  20-300     7525 SBL                                                                              89.6                                                                              250                               7430 3.16                                                                              5.16                                                                             2    68  50-100                                                                            irregular shape                                                                      7432 SBL                                                                              didn't                                                                            --                                                                        initiate                                                              7445 NBL                                                                              89.3                                                                              63                                7414.sup.(1)                                                                       3.87                                                                              5.60                                                                             0.25 20  50-200                                                                            irreguar shape                                                                       7428 NBL                                                                              89.2                                                                              3.3                               7290 3.87                                                                              1.93                                                                             6    12  50-300                                                                            round shape                                                                          7526 SBL                                                                              84.2                                                                              >100                              SUBSURFACE FEED                                                               7505 0.94                                                                              1.65                                                                             2    11  <250       7506 SBL                                                                              89.3                                                                              100                               7513 1.01                                                                              1.52                                                                             2     9  >200                                                                              large  7515 SBL                                                                              88.5                                                                              100                               7497 1.41                                                                              1.65                                                                             3    13  <150       7500 SBL                                                                              87.8                                                                              100                               plant                                                                              --  -- --   --  <50        7473 SBL                                                                              89.5                                                                              100                               __________________________________________________________________________     .sup.(1) 0.5 Liter run                                                   

We claim:
 1. A process for producing atmospherically stable alkali metalparticles comprising heating, in an inert atmosphere, an alkali metalselected from the group consisting of sodium and lithium in ahydrocarbon oil to a temperature above the melting point of the alkalimetal, agitating the metal in hydrocarbon oil mixture, under dispersionconditions, which mixture optionally contains a dispersing agent,contacting the molten metal-hydrocarbon oil dispersion mixture, above orbelow its surface, for at least one minute while the mixture is beingagitated under dispersion conditions, with at least 0.3 weight percentof anhydrous carbon dioxide, based on the weight of the alkali metal andcooling the alkali metal dispersion to below the melting point of thealkali metal to produce coated alkali metal particles dispersed in oil.2. The process of claim 1 further comprising filtering the cooled alkalimetal dispersed particles of claim 1 to remove the bulk of thehydrocarbon oil, washing the filtered dispersed particles with a lowboiling liquid hydrocarbon to remove the remainder of the oil, andrecovering hydrocarbon wet alkali metal coated particles.
 3. The processof claim 2 further comprising drying the hydrocarbon wet alkali metalparticles to produce dry alkali metal coated particles in the form ofpowders.
 4. The process of claim 1 where in the coated alkali metal islithium.
 5. The process of claim 1 wherein the anhydrous carbon dioxide,in an amount of between 0.3 and 5 weight percent based on the alkalimetal, is introduced below the surface of the dispersion of moltenalkali metal and hydrocarbon oil mixture while the mixture is beingagitated under dispersion conditions.
 6. The process of claim 1 whereinthe anhydrous carbon dioxide is passed through the molten alkalimetal-hydrocarbon oil mixture in an amount of between 0.3 and 5 weightpercent based on the alkali metal.
 7. The process of claim 1 in whichthe dispersing agent is oleic acid and the amount employed is in therange of 0.1 to 3.0% based on the alkali metal.
 8. Atmosphericallystable lithium metal particles having metal particle sizes within therange of 10 to 1000 microns which particles contain a protective surfacecoating composition comprising 0.1 to 0.3 atom percent lithium, 0.3 to0.4 atom percent carbon, and 0.3 to 0.5 atom percent oxygen. 9.Atmospherically stable coated lithium metal particles formed by heatinglithium metal in a hydrocarbon oil to a temperature above the meltingpoint of the lithium metal, agitating the the molten lithium, optionallyin the presence of a dispersing agent, maintaining agitation underconditions sufficient to disperse the lithium metal into small moltenparticles, while contacting the lithium metal-oil dispersion mixture,above or below its surface, with at least 0.3 weight percent ofanhydrous carbon dioxide for at least one minute to disperse the moltenlithium metal, and cooling the dispersion is to below the melting pointof the lithium metal, to produce alkali metal particles dispersed inoil.
 10. The atmospherically stable coated lithium metal particles ofclaim 9 further comprising being formed by filtering the dispersedparticles in oil to remove the bulk of the hydrocarbon oil, washing thefiltered alkali metal particles with a low boiling liquid hydrocarbon toremove residual oil, and drying the particles to recover stable coatedlithium metal particles having particle sizes in the range of 10 to 1000microns in the form of a dry powder.
 11. An atmospherically stable,coated lithium metal powder according to claim 10 having particle sizesbetween 10 and 300 microns in size.
 12. The atmospherically stable,coated lithium metal powder of claim 10 isolated in a low boilingnormally liquid hydrocarbon.
 13. The atmospherically stable, coatedlithium metal particles of claim 10, wherein the process for formingsaid particles further comprises after said drying step washing themetal with a low boiling liquid hydrocarbon solvent, and drying thepowder.
 14. Atmospherically stable, coater sodium metal particles formedby heating sodium metal in a hydrocarbon oil to a temperature above themelting point of the sodium metal, agitating the the molten sodium,optionally in the presence of a dispersing agent, maintaining agitationunder conditions sufficient to disperse the sodium metal into smallmolten particles, while contacting the sodium metal in the dispersionmixture, above or below its surface, with at least 0.3 weight percent ofanhydrous carbon dioxide for at least one minute, and cooling thedispersion to below the melting point of the sodium, to produce coatedalkali metal particles dispersed in oil.
 15. The atmospherically stable,coated sodium particles of claim 14, wherein the process for formingsaid particles further comprises after said cooling step recovering thestable, coated sodium particles by filtering the dispersed particles inoil to remove the bulk of the hydrocarbon oil, washing the filteredalkali metal particles with a low boiling liquid hydrocarbon to removeresidual oil, and drying the particles to recover stable coated sodiummetal particles having particle sizes in the range of 10 to 1000 micronsin the form of a dry powder.
 16. An atmospherically stable, coatedsodium metal powder is according to claim 15 having particle sizesbetween 10 and 300 microns in size.
 17. The atmospherically stable,coated sodium metal powder of claim 15 isolated in a low boilingnormally liquid hydrocarbon.
 18. The atmospherically stable, coatedsodium metal particles of claim 15, wherein the process of forming saidparticles further comprises after said drying step washing the meal witha low boiling liquid hydrocarbon solvent, and drying the powder.